1. Field of the Invention
The present invention relates to an inverter-integrated motor for an automotive vehicle, and more particularly relates to the improvement of its inverter section.
2. Description of the Background Art
To maintain the condition of an air-conditioning system when an engine is temporarily stopped during a short period of time (e.g., during a so-called “idling stop” operation), it is conventionally known that a motor-driven compressor is preferably employed for a refrigerating cycle system of an automotive vehicle. Furthermore, it is conventionally known that a motor section of the motor-driven compressor is cooled by a low-pressure coolant gas.
Furthermore, there is a conventional motor-driven compressor having an inverter section mounted thereon, which is already proposed for automotive vehicles. The inverter section is equipped for driving an alternating-current motor under supply of direct-current power. More specifically, this conventional inverter-integrated motor-driven compressor includes a motor section and a compressor section which are connected in an axial direction. An inverter section is fixed to an end surface of the motor section opposed to the compressor section. The inverter section includes three-phase inverter modules for converting DC (direct-current) power into three-phase AC power and supplying the converted AC motor to the motor section, a smoothing capacitor for suppressing DC current ripples of the thee-phase inverter modules, a printed circuit board mounting a controller IC for intermittently controlling switching elements of the three-phase inverter modules and also mounting a power source IC, and a heat sink fixed to the bottom of the three-phase inverter circuit IC.
However, according to the above-described conventional inverter-integrated motor-driven compressor for an automotive vehicle, the motor section and the compressor section are arranged in the axial direction. The axial length of the apparatus tends to become long. It is hence difficult to replace the conventional belt-driven compressor by the above-described inverter-integrated motor-driven compressor. In other words, when the above-described inverter-integrated motor-driven compressor is installed in an engine room, it is necessary to change the layout of various devices to be placed in the engine room. The processes and the costs will increase.
Furthermore, the engine room capacity or volume available for the devices associated with the engine tends to decrease. The inverter-integrated motor-driven compressor needs to reduce its size and weight.
Furthermore, the three-phase inverter modules of the inverter section definitely require a proper cooling system. It was however difficult to cool the inverter section when it is placed adjacent to the motor section. More specifically, according to the conventional inverter-integrated motor-driven compressor, a cooling fan is fixed to a rotor to convey the cooling air into various portions in the motor section. Or, the motor section is cooled by a low-pressure coolant gas. However, it is not easy to effectively guide or introduce the cooling air or the low-temperature coolant gas toward the inverter section in the axial direction via a branched or bent route or passage of flow.
To solve the above problems, it will be possible to provide the inverter section on a housing, especially on an outer surface of the cylindrical wall of the motor section. However, in this case, it is necessary to dispose all of the circuit components on the outer surface of the cylindrical wall of the motor section. The circuit components include the power switching elements, the smoothing capacitor, and the control circuit constituting the three-phase circuit as well as numerous wiring for the use of power and control. This will necessarily increase the circumferential and axial size of the apparatus. The wiring work will become complicated. The increase in wiring length will induce the increase in wiring inductance and wiring resistance.
The above-described problems are not limited to the inverter-integrated motor-driven compressors and are also inherent to all of the inverter-integrated motors for automotive vehicles. The downsizing of the inverter section is hence earnestly required for the inverter-integrated motors for automotive vehicles. Especially, in addition to the downsizing, assuring anti-vibration properties is very important for the inverter-integrated motors for automotive vehicles. For example, the wiring of the inverter section is definitely required to secure adequate gap so as not to cause electrical short-circuit problems in the event of car crash. In this respect, there is a limit in realizing a high-density wiring, i.e., in realizing the downsizing of the inverter section.